Originally Posted by forrestinmathews

So Jim Cirillo killed a lot of people in gunfights as a member of the NYPD Stakeout Squad and learned a lot doing it. They had 13" Ithaca 37's loaded up with 2 slugs and 3 OO Buck by night with the theory that they could engage point targets inside and then keep the shot for outside in the darkness. By day the three buckshot came first and the slugs last figuring that the inside would be less crowded and the streets would require a higher level of precise shooting. I got most of this from page 32 of Jim Cirillo's Tales of the Stakeout Squad.

There's my best attempt at making a reasonable case for various setups. The best answer is because you can.